Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$121.35	4.777%	$127.1469	$127.15	$127.15	$127.10
Purchase #2	$10.94	5.333%	$11.5234	$11.52	$11.50	$11.50
Purchase #3	$67.27	10.835%	$74.5587	$74.56	$74.55	$74.60
Purchase #4	$207.88	8.479%	$225.5061	$225.51	$225.50	$225.50
Purchase #5	$83.67	9.821%	$91.8872	$91.89	$91.90	$91.90
Purchase #6	$185.70	12.604%	$209.1056	$209.11	$209.10	$209.10
Purchase #7	$107.89	5.341%	$113.6524	$113.65	$113.65	$113.70
7 purchase totals =	$784.70		$853.3803	$853.39	$853.35	$853.40